TGF-beta activators and TGF-beta production stimulators are employed to maintain or increase vessel lumen diameter in a diseased or injured vessel of a mammal. Conditions such as restenosis following angioplasty, vascular bypass grafts, transplanted organs, atherosclerosis or hypertension are characterized by a reduced vessel lumen diameter. In a preferred embodiment of the invention, TGF-beta activators and production stimulators inhibit abnormal proliferation of smooth muscle cells. TGF-beta activators or production stimulators that are not characterized by an undesirable systemic toxicity profile at a prophylactic dose are also amenable to chronic use for prophylactic purposes with respect to disease states involving proliferation and/or migration of vascular smooth muscle cells over time. Further provided is a method for determining TGF-beta in vitro, thereby identifying a patient at risk for atherosclerosis and monitoring a recipient that has received one or more administrations of a TGF-beta activator or production stimulator.